The present invention relates to an azeotropic like composition comprising 95 to 93% (% by weight) of tetrachlorodifluoroethane (hereinafter referred to as "Flon-112") and 5 to 7% of isooctane. The composition has a boiling point of 92.5.degree. to 92.7.degree. C.
Recently, importance of washing process is increasing with advance in miniturization and precision of parts in electronic field. For washing them, chlorofluorohydrocarbon solvents are employed because of their various advantages such as incombustibility, low toxity and selective solubility that they can dissolve fats, oils, grease and the like without erosion of high molecular compounds such as rubbers and plastics.
Examples of the chlorofluorohydrocarbon solvents used for washing are trichlorotrifluoroethane (hereinafter referred to as "Flon-113") which is chemically stable and safe, an azeotropic mixed solvent thereof and the like.
When temporarily fixing silicon wafers used for semiconductors, quartz, ceramics and the like in their processing such as cutting or polishing, waxes are used. Removal of the waxes by dissolving or peeling off, however, is essentially impossible by employing Flon-113 or an admixtures thereof because Flon-113 has a relatively low boiling point of 47.6.degree. C.
Flon-112 is a suitable solvent to the waxes of a relatively high melting point used for the temporary fixing because Flon-112 has a high boiling point of 92.8.degree. C. However, since Flon-112 has a high freezing point and becomes solid at a low temperature, it is hard to use in winter season, which limits width of its use. In addition, Flon-112 cannot be used as an extraction solvent for purifying waxes having a high melting point such as bees wax and Japan wax, because Flon-112 becomes solid on cooling.
Heretofore though there has been proposed a method for lowering the freezing point of Flon-112 in which various organic solvents such as alcohols, ketones or esters are admixed with Flon-112 to form mixed solvents of two-component system or three-component system which include an azeatropic system, many solvents obtained by the method sacrifice one or more useful advantageous properties of Flon-112. That is, those solvents are chemically unstable, flammable, or have a relatively high toxity. Azeotropic solvents of Flon-112 with solvents having a high solubility have a danger that they harm materials made of rubbers or plastics.
The present invention has done to provide an azeotropic like composition which can solve the disadvantages derived from the high freezing point of Flon-112 while keeping the above-mentioned excellent properties of Flon-112, and does not harm materials made of rubbers or plastics, and also is incombustible, chemically stable, and has an essentially constant boiling point.